1. Field of the Invention
The present invention relates to an illumination unit of a stereomicroscope, which is attached to the end of an objective of a stereomicroscope to enable coaxial vertical illumination and episcopic illumination.
2. Description of the Related Art
As a method of reflected light illumination of a stereomicroscope, episcopic illumination and coaxial vertical illumination are generally used. In episcopic illumination method, illumination light is illuminated episcopicly to a sample. To realize a episcopic illumination method, irradiate a sample by using a lamp or fiber from the outside of the observation optical axis of a stereomicroscope. The outside of the observation optical axis of a stereomicroscope is for example the side of a stereomicroscope or the inside of a stand for holding and focusing a stereomicroscope.
A coaxial vertical illumination method is used for obtaining an observation image of a sample clear to the depths without a shadow, or for obtaining an observation image free from insufficient intensity in incident light to an observation optics when observing a highly reflective sample. In a coaxial vertical illumination method for obtaining these observation images, the observation optical axis and illumination optical axis of a stereomicroscope are aligned.
A coaxial vertical illumination unit is necessary for realizing coaxial vertical illumination in a stereomicroscope. The technology of a coaxial vertical illumination unit is described in Jpn. UM Appln. KOKAI Publication No. 2527158 and Jpn. Patent Appln. KOKAI Publication No. 63-10408, for example. The Jpn. UM Appln. KOKAI Publication No. 2527158 describes that a semi-transparent mirror is provided in a microscope to make the microscope exclusive for coaxial vertical illumination to be realized. The Jpn. Patent Appln. KOKAI Publication No. 63-10408 describes that coaxial vertical illumination is realized by providing a coaxial vertical illumination unit removably at the end of an objective.